Viewed at night from the southern Port Hills, the centre of Christchurch appears as a dark smudge among the suburban lights. Almost a year after the earthquake that killed 185 people in New Zealand's second largest city, much of the central business district remains in the "red zone", cordoned-off and uninhabited but for the work crews that pass through the security gates each day in their hundreds.

This building site enclave is a strange echo of the city that stood there before it was thrust upwards and sideways by the 6.3-magnitude quake just before 1pm on 22 February 2011. Blinker your eyes and parts of the city appear untouched. But look to either side and the picture is of demolition work.

The broken shell of ChristChurch Cathedral, this South Island city's most famous landmark, stands deconsecrated and uncertain in a central square that grows bigger by the day, as demolition booms peck away at the surrounding buildings.

In empty lots where buildings were bowled over, waist-high weeds grow from the cracks. Billboards are frozen in time, promoting events for March 2011.

So familiar have tremors become in Christchurch that locals are unnervingly good at instantly estimating the magnitude of an earthquake. They have had plenty of practice. Since the 7.1 quake in September 2010 – the first and biggest, which caused no fatalities in part thanks to its arrival in the middle of the night – geologists have measured more than 10,000 earthquakes in the region.

Of those, more than 400 have registered over magnitude 4.0; more than 40 have surpassed 5.0. A cluster of three earthquakes measuring up to 6.0 struck two days before Christmas, causing fresh damage to buildings, including the cathedral, and closing the airport.

Days later, the state geological agency predicted that the area could expect aftershocks to continue for more than two decades, albeit with the likelihood of diminishing severity.

From his sixth-floor office on the edge of the red zone, Roger Sutton, chief executive of the Christchurch Earthquake Recovery Authority, lays out a map of the central city, with buildings shaded in black and grey that have been, or are likely to be, demolished. "You can see it's pretty extraordinary really," he says. Sutton, who impressed Cantabrians with his enthusiastic and engaged response to the February earthquake, when he was chief executive of the local power company, took a hefty pay cut to join the government agency. He remains upbeat.

"The level of destruction that we've got there is such that we've actually got an opportunity to do something really fresh," he says. "And people are feeling optimistic now. What we had before was just mishmash from historical accident, so to speak. Now we can think about it much more carefully and do something much, much better."

Rescue workers search the rubble of a building in Christchurch in February 2011. Photograph: Shuzo Shikano/AP

It is impossible to gauge how many people have left Christchurch for good. Predictions of a mass exodus have proved unfounded. An estimated departure of 10,000 could soon be offset by the arrival of workers, including from Ireland, lured by the appeal of a rebuild costing up to $30bn (£15.5bn).

With unemployment only slightly increased, and encouraging turnover at the port and airport, there is reason to remain positive, Sutton says. "The economy is still going gangbusters here. So despite the fact we have had a massive earthquake, and a large part of the central business district is still shut, all the economic indicators are actually positive."

He believes 2012 will be a "defining year" for the city and points to the rebirth of Cashel mall's shops, the newly opened Court Theatre and a soon-to-open 18,000-seat rugby stadium.

Together with the much admired Gap Filler community initiative, which illuminates vacant sites with everything from fun fairs to bicycle-powered cinemas, such projects have clearly encouraged residents.

Shipping containers have become the all-purpose emblem for the city. The Cashel mall has been built from them. They form makeshift braces for celebrated older buildings such as the cathedral. And they worm their way, stacked two-high, beneath the steep cliff on the road out to Sumner, protecting drivers from the ongoing landslides. Above, the frames of luxury homes lurch drunkenly from retreating foundations.

Sumner was among the worst-hit areas a year ago. The seaside village, less than four miles to the east of the epicentre, was pounded by falling rocks and landslides. Water, electricity and sewage systems were cut off for days.

Today, character is returning to the suburb. "I think there's huge opportunity here," says Karen Sheridan, who has opened a furniture store comprising two brightly painted shipping containers.

"The city's changed now, there's more focus out in the suburbs. Sumner was always very much a destination anyway, especially in the weekends and over summer. That's coming back. Things like this are helping to draw people to the area. But it's going to take a long time.

"People are sick of the earthquakes, the constant aftershocks. But we've all learned to get on with it. After February last year, the place was shut. It was like a desert. There was no one around. All the women and children left, and it was basically all full of men.

"I've been very, very lucky. Our house wasn't too badly damaged and I haven't had to move out. But a lot of my friends are having big trouble with their insurance companies, and struggling to move on. A lot of people are still stuck back in that day in February."

But the mood in Christchurch is hardly one of unified optimism. Disaffection with the pace of recovery, especially in the eastern suburbs where thousands of homes are unsafe, is high.

Months of building frustration found a lightning rod in the recent decision of the city council to award its chief executive a $68,000 (£35,000) pay rise – a decision that in the circumstances "bordered on wilful ignorance", according to the Christchurch Press.

Even after he agreed to forgo the increase, a protest calling for his resignation, along with that of the mayor, Bob Parker, the former TV host who had been so lauded in the months after the February disaster, attracted more than 4,000 people a fortnight ago.

Leanne Curtis, spokeswoman for CanCern, a network of residents' groups, says people need to see firm timetables for the restoration of their homes and community facilities. "Without that you become a very depressed city," she says. "It's a very bad place for us to be mentally – you can't build, innovate, be entrepreneurial. You lose motivation, capacity to get up and help ourselves. You can't remake a city out of depression."

Communities in the east, and especially those which still await a government decision on whether their land is viable for rebuilding, are boiling over with frustration – with the insurance companies, with the authorities and with a sense of being overlooked, says Curtis.

While roads have been patched up in most of the city's suburbs, in parts of the residential red zone bordering the Avon river as it snakes from the CBD to the coast, streets still betray the bumps and fissures of the 2011 earthquake.

The approaching anniversary is weighing heavy on people's minds, she says, with any adrenalin from the early recovery period having long drained away.

"There's none of this 'we're so resilient, we're so strong' from anybody on the ground," says Curtis. "In the east, people don't feel resilient, they feel tired, frustrated, like nothing's happening. There is very little vision, very little leadership, very little co-ordination."